/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.giraph.edge;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;

/**
 * Interface for data structures that store out-edges for a vertex.
 *
 * @param <I> Vertex id
 * @param <E> Edge value
 */
public interface VertexEdges<I extends WritableComparable, E extends Writable>
    extends Iterable<Edge<I, E>>, Writable {
  /**
   * Initialize the data structure and set the edges from an iterable.
   * This method (or one of the two alternatives) must be called
   * after instantiation, unless readFields() is called.
   * Note: whether parallel edges are allowed or not depends on the
   * implementation.
   *
   * @param edges Iterable of edges
   */
  void initialize(Iterable<Edge<I, E>> edges);

  /**
   * Initialize the data structure with the specified initial capacity.
   * This method (or one of the two alternatives) must be called
   * after instantiation, unless readFields() is called.
   *
   * @param capacity Initial capacity
   */
  void initialize(int capacity);

  /**
   * Initialize the data structure with the default initial capacity.
   * This method (or one of the two alternatives) must be called
   * after instantiation, unless readFields() is called.
   *
   */
  void initialize();

  /**
   * Add an edge.
   * Note: whether parallel edges are allowed or not depends on the
   * implementation.
   *
   * @param edge Edge to add
   */
  void add(Edge<I, E> edge);

  /**
   * Remove all edges to the given target vertex.
   * Note: the implementation will vary depending on whether parallel edges
   * are allowed or not.
   *
   * @param targetVertexId Target vertex id
   */
  void remove(I targetVertexId);

  /**
   * Return the number of edges.
   *
   * @return Number of edges
   */
  int size();
}
